Recalculate column heights as part of column set layout.

third_party/WebKit/Source/core/layout/LayoutMultiColumnFlowThread.h

 /*
  * Copyright (C) 2012 Apple Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 165 matching lines @@
 
     LayoutMultiColumnSet* columnSetAtBlockOffset(LayoutUnit) const final;
 
     void layoutColumns(SubtreeLayoutScope&);
 
     // Skip past a column spanner during flow thread layout. Spanners are not laid out inside the
     // flow thread, since the flow thread is not in a spanner's containing block chain (since the
     // containing block is the multicol container).
     void skipColumnSpanner(LayoutBox*, LayoutUnit logicalTopInFlowThread);
 
-    bool recalculateColumnHeights();
+    // Returns true if at least one column got a new height after flow thread layout (during column
+    // set layout), in which case we need another layout pass. Column heights may change after flow
+    // thread layout because of balancing. We may have to do multiple layout passes, depending on
+    // how the contents is fitted to the changed column heights. In most cases, laying out again
+    // twice or even just once will suffice. Sometimes we need more passes than that, though, but
+    // the number of retries should not exceed the number of columns, unless we have a bug.
+    bool columnHeightsChanged() const { return m_columnHeightsChanged; }
+    void setColumnHeightsChanged() { m_columnHeightsChanged = true; }
 
     void columnRuleStyleDidChange();
 
     // Remove the spanner placeholder and return true if the specified object is no longer a valid spanner.
     bool removeSpannerPlaceholderIfNoLongerValid(LayoutBox* spannerObjectInFlowThread);
 
     LayoutMultiColumnFlowThread* enclosingFlowThread() const;
     FragmentationContext* enclosingFragmentationContext() const;
     LayoutUnit blockOffsetInEnclosingFragmentationContext() const { ASSERT(enclosingFragmentationContext()); return m_blockOffsetInEnclosingFragmentationContext; }
 
@@ skipping 39 matching lines @@
     // top location estimates (due to e.g. margin collapsing), and possibly for other reasons.
     LayoutMultiColumnSet* m_lastSetWorkedOn;
 
     unsigned m_columnCount; // The used value of column-count
     LayoutUnit m_columnHeightAvailable; // Total height available to columns, or 0 if auto.
 
     // Cached block offset from this flow thread to the enclosing fragmentation context, if any. In
     // the coordinate space of the enclosing fragmentation context.
     LayoutUnit m_blockOffsetInEnclosingFragmentationContext;
 
-    bool m_inBalancingPass; // Set when relayouting for column balancing.
-    bool m_needsColumnHeightsRecalculation; // Set when we need to recalculate the column set heights after layout.
+    bool m_columnHeightsChanged; // Set when column heights are out of sync with actual layout.
     bool m_progressionIsInline; // Always true for regular multicol. False for paged-y overflow.
     bool m_isBeingEvacuated;
 };
 
 // Cannot use DEFINE_LAYOUT_OBJECT_TYPE_CASTS here, because isMultiColumnFlowThread() is defined in
 // LayoutFlowThread, not in LayoutObject.
 DEFINE_TYPE_CASTS(LayoutMultiColumnFlowThread, LayoutFlowThread, object, object->isLayoutMultiColumnFlowThread(), object.isLayoutMultiColumnFlowThread());
 
 } // namespace blink
 
 #endif // LayoutMultiColumnFlowThread_h